Featured Research

from universities, journals, and other organizations

Gullies On Mars Show Tantalizing Signs Of Recent Water Activity

Date:

March 2, 2009

Source:

Brown University

Summary:

Planetary geologists have located a gully system on Mars that appears to have been carved by melt water that originated in nearby snow and ice deposits. The gullies, which were determined to be about 1.25 million years old, may represent the most recent period when water flowed on the planet.

Planetary geologists at Brown University have found a gully fan system on Mars that formed about 1.25 million years ago. The fan offers compelling evidence that it was formed by melt water that originated in nearby snow and ice deposits and may stand as the most recent period when water flowed on the planet.

Related Articles

Gullies are known to be young surface features on Mars. But scientists studying the planet have struggled with locating gullies they can conclusively date. In a paper that appears on the cover of the March issue of Geology, the Brown geologists were able to date the gully system and hypothesize what water was doing there.

The gully system shows four intervals where water-borne sediments were carried down the steep slopes of nearby alcoves and deposited in alluvial fans, said Samuel Schon, a Brown graduate student and the paper's lead author.

"You never end up with a pond that you can put goldfish in," Schon said, "but you have transient melt water. You had ice that typically sublimates. But in these instances it melted, transported, and deposited sediment in the fan. It didn't last long, but it happened."

The finding comes on the heels of discoveries of water-bearing minerals such as opals and carbonates, the latter of which was announced by Brown graduate student Bethany Ehlmann in a paper in Science in December. Those discoveries build on evidence that Mars was occasionally wet far longer than many had believed, and that the planet may have hosted a warm, wet environment in some places during its long history.

However, the finding of a gully system, even an isolated one, that supported running water as recently as 1.25 million years ago greatly extends the time that water may have been active on Mars. It also adds to evidence of a recent ice age on the planet when polar ice is believed to have been transported towards the equator and settled in mid-latitude deposits, said James Head III, professor of geological sciences at Brown, who first approximated the span of the martian ice age in a Nature paper in 2003.

"We think there was recent water on Mars," said Head, who with Brown postdoctoral researcher Caleb Fassett is a contributing author on the paper. "This is a big step in the direction to proving that."

The gully system is located on the inside of a crater in Promethei Terra, an area of cratered highlands in the southern mid-latitudes. The eastern and western channels of the gully each run less than a kilometer from their alcove sources to the fan deposit.

Viewed from afar, the fan appears as one entity several hundred meters wide. But by zooming in with the HiRISE camera aboard the Mars Reconnaissance Orbiter, Schon was able to distinguish four individual lobes in the fan, and determine that each lobe was deposited separately. Moreover, Schon was able to identify the oldest lobe, because it was pockmarked with small craters, while the other lobes were unblemished, meaning they had to be younger.

Next came the task of trying to date the secondary craters in the fan. Schon linked the craters on the oldest lobe to a rayed crater more than 80 kilometers to the southwest. Using well-established techniques, Schon dated the rayed crater at about 1.25 million years, and so established a maximum age for the younger, superimposed lobes of the fan.

The team determined that ice and snow deposits formed in the alcoves at a time when Mars had a high obliquity (its most recent ice age) and ice was accumulating in the mid-latitude regions. Sometime around a half-million years ago, the planet's obliquity changed, and the ice in the mid-latitudes began to melt or, in most instances, changed directly to vapor. Mars has been in a low-obliquity cycle ever since, which explains why no exposed ice has been found beyond the poles.

The team tested other theories of what the water may have been doing in the gully system. The scientists ruled out groundwater bubbling to the surface, Schon said, because it seemed unlikely to have occurred multiple times in the planet's recent history. They also don't think the gullies were formed by dry mass wasting, a process by which a slope fails as in a rockslide. The best explanation, Schon said, was the melting of snow and ice deposits that created "modest" flows and formed the fan.

More From ScienceDaily

More Space & Time News

Featured Research

Mar. 31, 2015 — Designed to detect the fossil radiation of the Universe, the Planck satellite, working in tandem with Herschel, can also help to understand the macrostructure of the Universe. A just-published ... full story

Mar. 31, 2015 — Astronomers have conducted observations of the massive-star forming region IRAS 16547-4247. The observation results shows the presence of multiple, or at least two, gas outflows from a protostar, ... full story

Mar. 30, 2015 — Stars form when gravity pulls together material within giant clouds of gas and dust. But gravity isn't the only force at work. Both turbulence and magnetic fields battle gravity, either by stirring ... full story

Mar. 30, 2015 — Scientists have long puzzled over the planet Mercury's excessively dark surface. New research suggests that carbon from passing comets could be the planet's mystery darkening ... full story

Mar. 30, 2015 — Luke Skywalker's home in "Star Wars" is the desert planet Tatooine, with twin sunsets because it orbits two stars. So far, only uninhabitable gas-giant planets have been identified circling such ... full story

Mar. 26, 2015 — Astronomers have studied how dark matter in clusters of galaxies behaves when the clusters collide. The results show that dark matter interacts with itself even less than previously thought, and ... full story

Mar. 26, 2015 — The best observations so far of the dusty gas cloud G2 confirm that it made its closest approach to the supermassive black hole at the centre of the Milky Way in May 2014 and has survived the ... full story

Mar. 25, 2015 — Researchers have completed a new analysis of an ancient Martian lake system in Jezero Crater, near the planet's equator. The study finds that the onslaught of water that filled the crater was one of ... full story

Mar. 25, 2015 — The precise measurement of Saturn's rotation has presented a great challenge to scientists, as different parts of this sweltering ball of hydrogen and helium rotate at different speeds whereas its ... full story

Related Stories

Jan. 28, 2015 — Gullies carved into impact craters on Mars provide a window into climate change on the Red Planet. A new analysis suggests Mars has undergone several ice ages in the last several million years. The ... full story

July 10, 2014 — Repeated high-resolution observations made by NASA's Mars Reconnaissance Orbiter (MRO) indicate the gullies on Mars' surface are primarily formed by the seasonal freezing of carbon dioxide, ... full story

Apr. 25, 2014 — New research has shown that there was liquid water on Mars as recently as 200,000 years ago. The southern hemisphere of Mars is home to a crater that contains very well-preserved gullies and debris ... full story

Nov. 16, 2012 — Near surface water has shaped the landscape of Mars. Areas of the planet’s northern and southern hemispheres have alternately thawed and frozen in recent geologic history and comprise striking ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.